Gradle Build: look for secp256k1 in ~/.nix-profile/lib

This removes the need to use hard-coded paths.

README.adoc

@@ -59,13 +59,15 @@ We are currently using a Nix flake to install the native `libsecp256k1` and usin
 
 If necessary copy updated, extracted headers into `src/main/java/org/consensusj/secp256k1/`
 
+Make sure you have installed the current version of `secp256k1` with `nix profile install nixpkgs#secp256k1`
+
 . `./gradlew build`
 
 == Running with Gradle Wrapper
 
 (This assumes a specific hash/version of secp256k1 was installed with nixpkgs)
 
-. `./gradlew -PjavaPath="/nix/store/j9mf1fh4wbb8c3x1zwqfs218bhml1rbw-secp256k1-0.4.0/lib/" secp256k1-examples-java:run`
+. `./gradlew secp256k1-examples-java:run`
 
 == Building with Nix
 

build.gradle

@@ -27,7 +27,8 @@ subprojects {
 
     test {
         useJUnitPlatform()
-        systemProperty "java.library.path", findProperty("javaPath") ?: "/nix/store/j9mf1fh4wbb8c3x1zwqfs218bhml1rbw-secp256k1-0.4.0/lib/"
+        def userHome = System.getProperty("user.home")
+        systemProperty "java.library.path", findProperty("javaPath") ?: "${userHome}/.nix-profile/lib"
         jvmArgs += '--enable-preview'
         jvmArgs += '--enable-native-access=ALL-UNNAMED'
     }

secp256k1-examples-java/build.gradle

@@ -30,5 +30,6 @@ application {
 }
 
 run {
-    systemProperty "java.library.path", findProperty("javaPath") ?: ""
+    def userHome = System.getProperty("user.home")
+    systemProperty "java.library.path", findProperty("javaPath") ?: "${userHome}/.nix-profile/lib"
 }

secp256k1-examples-kotlin/build.gradle

@@ -15,6 +15,7 @@ application {
 }
 
 run {
-    systemProperty "java.library.path", findProperty("javaPath") ?: ""
+    def userHome = System.getProperty("user.home")
+    systemProperty "java.library.path", findProperty("javaPath") ?: "${userHome}/.nix-profile/lib"
 }